Rob Stewart wrote:
From: John Nagle <nagle@animats.com>
I've done some cleanup on my version of fixed_string at
This now conforms to Dunn's decision on length, i.e.
"fixed_string<char,4> s" now has space for four characters plus a trailing null.
Good.
I decided that "operator[]" had to let users reach the trailing null without a subscript error, so that the classic C idiom of a loop stopped by the trailing null
for (i=0; s[i]; i++)
Good idea.
would still work. Because "operator[]" can't tell a read from a write, this offers the possibility of overstoring the
Sure it can: just return a proxy. Assignment through the proxy is a write and can be checked against exceeding N. Conversion of the proxy to the character type is a read and can permit accessing element N + 1.
Returning a proxy object adds complexity to a very low level operation, which may not be a good idea. I'm struggling to keep this rather simple object as simple as possible. There's also the problem that the proxy object would have to be on the stack. Consider char_string<16> s("0123456789ABCDEF"); char& hexchar(int n) { return(s[n]); } Either we pass back a proxy object by value, which is expensive, or we pass a reference to a local object, which is wrong. Or we just pass a char, which is what people expect. I don't want to get too clever here.
Will you still need to reset the trailing null if using the proxy?
Some trailing null maintenance is necessary, because you can mix C++ and C operations. For example; char_string<72> s = "Hello"; s += '.' // add period printf("%s\n",s.c_str()); Currently, every use of "operator[]" invalidates the length. John Nagle Team Overbot